The present invention relates to a belt unit capable of enhancing the meandering prevention of an endless belt and also to an image forming apparatus equipped with the belt unit.
Conventionally, as driving rollers that drive an endless belt used for equipment such as OA (Office Automation) equipment, for example, driving rollers that include a roller body and elastic rubber that wound around the surface of the roller body had been known.
In recent years, however, improvement in the speed and colorization of copying machines, laser beam printers (LBP), and the like has been developed, so that the above mentioned driving rollers with the endless belt, due to the variation in the speed of feeding the endless belt by the driving roller and the irregularities of the surface of the endless belt, have problems such as character skew, image stretch, and color deviation. Thus, the dimensional precision of the driving roller and the driving precision of the belt have been very crucial.
In an attempt to solve such problems, as the driving rollers for the OA equipment, driving rollers that include sponge-typed elastic rubber that is wound around the roller body have been disclosed (see Japanese Laid-Open Patent Publication 2010-152063, for example).
However, in Japanese Laid-Open Patent Publication 2010-152063, a guide rib disposed in the endless belt is likely to overrun on the driving roller for an extended time. This is because the whole external peripheral surface of the driving roller disclosed in Japanese Laid-Open Patent Publication 2010-152063 is wound with sponge typed elastic rubber and the elastic rubber is entirely made of a material having a high friction coefficient.
In view of the problem described above, an object of the present invention is to provide a belt unit that can prevent a guide rib from overrunning on a driving roller for an extended time.